Dealing with Dew

Questions and answers about processing in StarTools and how to accomplish certain tasks.
Rkonrad
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Re: Dealing with Dew

Post by Rkonrad »

Hi Simon,

I gave your data a go omitting the S11 data to give a bi-colour image. The method was basically the same as the video I posted earlier (generally). To get the Oiii to come through I had to process the Ha and Oiii separately then recombined them. I had to do a wipe with the Oiii data using vignette to get rid of most of the anomalies then I masked the central area with "life" to emphasize the area even more ( a lot!). The result is not necessarily scientific but in my opinion the best option for this data. The stars are from Oiii. Sorry but the log file is unintelligible for me to post. Let me know if you want more details.

https://www.flickr.com/gp/rkonrad/FK6880

Richard
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Re: Dealing with Dew

Post by admin »

szymon wrote:
of course it doesn't remove them, which is also an option).
How would you get wipe to remove them?
Sorry, I meant using something like the Heal module. You'd do something similar to this for removing dust bunnies.
Rkonrad wrote:To get the Oiii to come through I had to process the Ha and Oiii separately then recombined them. (...) The result is not necessarily scientific but in my opinion the best option for this data.
Thanks Richard. This seems to exhibit the same problems in the highlights as the previous image you processed separately and combined afterwards;
Screenshot_2019-09-29 Wizard Nebula.png
Screenshot_2019-09-29 Wizard Nebula.png (128.59 KiB) Viewed 1103 times
I also couldn't help but notice there is a fair bit of nebulosity and detail at 8/9 o'clock that is not readily visible (example) in exposures comparable to or exceeding the ones quoted for this dataset....
Ivo Jager
StarTools creator and astronomy enthusiast
Rkonrad
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Joined: Sun Feb 07, 2016 2:55 am

Re: Dealing with Dew

Post by Rkonrad »

Thanks, I noticed that. This doesn't always happen in processing attempts using the same technique - this and the last being one of the few examples. Why does this happen?

Also, you're quite correct that the nebulocity to the left shouldn/t - doesn't exist! It must be a poor wipe for the Ha data. Perhaps I should have wiped with the narrowband setting and applied some aggressiveness.

Cheers Richard
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Re: Dealing with Dew

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Rkonrad wrote:Thanks, I noticed that. This doesn't always happen in processing attempts using the same technique - this and the last being one of the few examples. Why does this happen?

Also, you're quite correct that the nebulocity to the left shouldn/t - doesn't exist! It must be a poor wipe for the Ha data. Perhaps I should have wiped with the narrowband setting and applied some aggressiveness.

Cheers Richard
Combining processed channels can (and usually will) yield all manner artifacts. The artifacts depend on which operations were used on the individual frames. What is appropriate in luminance space is usually not at all appropriate in color space.

E.g. Let's take this image;
Image


I can modify the image in the luminance domain by re-stretching it, doing contrast enhancement, maybe some wavelet sharpening and it will still remain a valid black and white image with enhanced/modified detail;
Image


But if I do the same in individual channels and then recombine, I'd get this;
Image


The "colors" are purely artifacts, and no one (I presume) would claim they have brought out "latent" detail or nebulosity.
Ivo Jager
StarTools creator and astronomy enthusiast
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